Before structured concurrency, such code would run...

# coroutines

[louiscad]

Before structured concurrency, such code would run properly:

launch {
    val someWorkAsync = async {
        throw CustomException()
    }
    delay(100)
    try {
        someWorkAsync.await()
    } catch (e: CustomException) {
        println("Handled it! $e")
    }
}

If I understood correctly, now, the whole scope is cancelled, even though the exception is handled properly when calling await(). How can I get the previous behavior? Create a Job that has scope's job as parent, and use it for async(…) { … }?

[marstran]

I think you can use supervisorScope { } for that.

[Vsevolod Tolstopyatov [JB]]

async(SupervisorJob(coroutineContext[Job])) 😞

[Vsevolod Tolstopyatov [JB]]

but generally withContext should be used instead of single async.
And for multiple asyncs there is coroutineScope

[Vsevolod Tolstopyatov [JB]]

could you please share actual use-case with such pattern?

[elizarov]

Actually, there is a special code in the library that ensures that this particular pattern works as expected.

[elizarov]

Ah, sorry. I forgot about delay. It will throw CancellationException, so you will not be able to catch exception with await. Thanks @[removed] for pointing that out.

[louiscad]

The use case could be for when you pass the Deferred outside the coroutine, so you can await it somewhere else. I thought I used it for single line requestPermission(…) call on Android, but it turns out I use CompletableDeferred instead, so I think I have no use case at the moment.